1. USDA-ARS; Crop Science Research Laboratory; Genetics and Sustainable Agricultural Research Unit; Mississippi State MS 39762
2. Agronomy, Horticulture, and Plant Science Dep.; South Dakota State Univ.; Brookings SD 57006
3. USDA-ARS; Coastal Plains Soil, Water, and Plant Research Center; Florence SC 29501
4. Dep. Soil and Crop Sciences; Texas A&M Univ.; College Station TX 77843